The disclosure relates to precision robotics and, more specifically, calibration of robotic cells for relative positioning, such as home position of an industrial robot.
Manufacturing increasingly relies on industrial robots for improved efficiency, lowering costs, and systematic control and improvement of repeated tasks, such as assembly, testing, repair, distribution, disposal, etc. Many industrial robots include computer-controlled positioning systems that precisely position and track the location of robot activities, particularly with regard to their environment (commonly a cell) and/or a work object with which they interact. A robotic cell may be defined as an integrated robotic system that includes a robot, controller, and safety environment (often an enclosure or other defined space of some sort), and may include peripherals such as part positioners and devices for moving parts in and out of the cell. During operation a work object is generally present within the cell or moving into or out of the cell, unless the cell is idle or some maintenance, recovery, calibration, or other supporting activity is underway.
Many industrial robots include one or more actuators and related axes that position one or more tools mounted to the robot for use on a work object. These actuators may be controlled by one or more position controllers and servo loops to precisely position the actuators and, thereby, the tools relative to the work object and/or peripherals or features of the work environment. For example, an industrial coating robot may include a robotic arm featuring 4-6 joints with independent servomotors, such as a rotating base joint, a base pivot joint, an elbow pivot joint, a wrist rotating joint, a wrist pivot joint, and an end effector rotating joint. Because robots may change over time, it may be useful to be able to have periodic and/or event-based calibration of an industrial robot. For example, wearing of parts, changes in dimension tolerances, component replacement, and/or crashes can all create variations in positioning that may be calibrated out or otherwise compensated for.
Calibrating an industrial robot generally includes defining a home position (0, 0, 0 in an x, y, z coordinate system), instructing the robot positioning system to navigate to a desired location, then using one or more measurement tools or gauges to determine how far the actual location is from the desired location. This process can be repeated for a number of positions relative to the various axes and actuators of the robot to determine one or more correction factors that may be applied to robot positioning commands during operation.